Abstract: A relay supervision system is disclosed to check the presence and operability both of a relay and the associated circuitry located at a position remote from the control unit which effects the supervision. The supervision is accomplished by pulsing the relay with energy at a volt-time integral less than that required to energize the relay and displace a contact set, but sufficient to cause current flow through the winding and its associated circuit components. If the relay includes two separate windings, each winding can be separately pulsed at different times, the relay state determined, and both windings effectively supervised without changing the position of the contact sets operated by the windings.

Abstract: A security system provides for bidirectional communication between a controller and a plurality of addressable transponders. At least one transponder includes a sensor circuit for detecting motion, which motion is indicated by the transponder signalling back to the controller. During a walk test the controller sends a signal back to the transponder, completing the circuit for the visible output indicator so that subsequent motions during the walk test sequence will be immediately displayed at the transponder, without necessitating successive communication through the loop including the controller. In systems where the controller itself reports upwardly in a hierarchy of units, the walk test can confirm operability of the entire system, including other condition-indicating signals.

Abstract: A mounting frame for supporting several printed circuit boards in abutting relationship includes a pair of side frame members. At least some of the printed circuit boards have slots along or near the side edges, through which screws extend into the side frame members. The screw heads extend over and retain the printed circuit boards in position. When the screws are loosened for some of the boards, those boards can be displaced from each other but not removed from the frame. Additional loosening of one set of screws allows the removal of that one board, even if that board is not the last board in the run of boards. Cylindrical bores are provided in at least one of the side frame members to afford pivotal mounting of the frame-and-card set in an enclosure. When the frame-and-card assembly is pivoted outwardly, an additional set of cards can be mounted on the back of the frame.

Abstract: A security alarm system includes a transponder having a housing enclosing both a sensor and associated circuit means in a unitary package. The housing base includes barrel-shaped connectors, and a pc board carrying the communications components is carried by the housing cover. Flag-like connectors mate with the barrel-shaped connectors when the cover is attached to the base, and the connectors give both good mechanical indexing and retention, and effective electrical contact. Removal of the cover from the base breaks the electrical contact and thus breaks continuity back to the system controller, indicating someone has tampered with the system.

Abstract: A system for debouncing a switch circuit includes a sample circuit for providing an initial determination of the switch status, and a debounce circuit connected to operate on the output of the sample or sensing circuit to verify the actual switch status by providing a confirmation signal. The system of the invention accumulates a count related either to the rate at which the sample circuit operates, or the actual changes in state indicated by latches coupled to the sample circuit. If the count accumulates to a predetermined number before being cleared by a confirmation signal verifying the switch status, then the irregular operation is signalled. This identifies a continuous, rapid alternation between different switch states without a confirmation of an actual state change, which would otherwise be undetected by system operation.

Abstract: An alarm system includes a controller and a plurality of transponders having different addresses. Certain of the transponders include switch means for monitoring conditions, and latch circuits to retain memory of the switch conditions. The controller includes means for positive recognition of a latched alarm or trouble condition in any transponder, before the clear-alarm signal or clear-trouble signal is sent from the controller to restore the alarm circuits to their original states. This insures that an alarm or trouble condition at a transponder is not "missed" by inadvertent clearing before a positive recognition is registered in the controller.

Abstract: An independent transmitter/receiver, or a transponder in a communication system, receives signals distorted by outside, unwanted conditions such as noise, line capacitance, and so forth. The status of a switch is checked at periodic times, by pulsing, rather than by continuous current flow, to conserve power. The invention includes a debounce circuit for monitoring the switch status; the debounce circuit is adjusted by a debounce select signal received from outside the transmitter/receiver. In addition a sensing circuit is coupled between the switch being monitored and the debounce circuit. The sensing circuit also has its sensing operation adjusted as a function of the debounce select signal. This allows for accurate monitoring of the switch condition, notwithstanding noise, line capacitance and other factors.

Abstract: A security system for a protected premise has a controller which receives data, over a pair of line conductors, from the addressed transponder of a series of addressable transponders located within the protected premise and connected across the line. To enhance the security of the system and to prevent compromising, the data is sent to the controller in coded form that changes from time to time in accordance with a secret code schedule. A decoding or decrypting system in the controller operates in accordance and in step with the same secret code schedule to decode the received coded data to recover the original information. The coded data may represent an encrypted signature of the addressed transponder which signature is decrypted to check the validity of the replying transponder.

Abstract: A communication system in which a controller ordinarily polls addressable transponders in a sequential or random manner normally allows the transponders to respond only in their respective assigned time period. Certain of the transponders are connected to allow response in a predefined time segment from those transponders so connected if (1) the transponder is in fact programmed for response during this predefined time segment, and (2) the predefined time segment is now occuring. By providing the predefined time segment at the same position in the response time period of each transponder, a "public time" is provided to allow virtually instantaneous identification and verification of a high priority interrupt (such as a holdup alarm). In addition the transponders programmed to respond during public time on a high priority basis can be subdivided into separate groups, and the groups can be identified at the controller.

Abstract: A communications system includes a transmitter for sending successive composite signals, each of which has successive segments which represent different data. A composite signal can be a pulse group with the segments denoted by individual pulses. A plurality of receivers are connected to receive the successive composite signals and recognize the data in each signal. Part of the transmitted composite signal is encoded by modifying at least one segment of a given composite signal in a predetermined manner. When an addressed receiver detects the encoded data or key in the composite signal, the receiver assigns a different significance to data in the remainder of that composite signal, and/or in at least one other composite signal. If the key is present in the next successive transmission, yet another significance is assigned to the data.

Abstract: An information display is provided to denote both (1) specific events, such as alarm of a smoke detector or unauthorized entry into a building, and (2) the time elapsed between successive events. The event identification data are stored in conjunction with data representing the time elaspsed since the occurrence of the previous event. The display can be cleared, and reconstituted at a rate related to the original rate at which the events occurred, selected by the viewer. The information regarding events and time differences can be stored and saved in a memory external to the timed-replay portion of the system.

Abstract: The condition of a rechargeable battery, which is employed as a backup d-c power supply for a load in the event of an emergency and is normally charged by a d-c charging voltage through a series-connected protective fuse, is monitored by momentarily reducing the charging voltage and effectively sensing or measuring the voltage across the series-connected fuse and battery during the momentary reduction, while not affecting the load. If the battery is connected and is functioning properly and if the fuse is connected and is continuous, the sensed voltage will exceed a predetermined desired threshold level, and this normal condition may be visually and/or audibly indicated. On the other hand, if the battery is disconnected, or if the battery voltage is abnormally low, or if the fuse is absent or is open, then the sensed voltage will fall below the desired threshold level, signifying a trouble condition. When such a condition is detected, a trouble indicator provides an appropriate visual and/or audible signal.

Abstract: The integrity of a two-conductor transmission line, over which d-c energizing voltage is supplied to a series of shunt-connected detectors (such as fire and/or smoke detectors) and which line is terminated by an end-of-line capacitor, is monitored and repetitively tested by periodically and momentarily interrupting the application of the d-c energizing voltage to the transmission line or conductor pair, while at the same time connecting a resistive load across the line's input end to provide a discharge path for the capacitor. If the integrity is normal, meaning that the line is continuous and not open, and has no excessively high series resistance or excessively low shunt resistance, and also meaning that the capacitor is functioning normally and is not deteriorated, the capacitor will discharge very little during each test and will maintain a relatively high voltage across the resistive load.

Abstract: A Communication System useful for fire detection which transfers data/commands bidirectionally between a controller and connected transponders on a real time, interactive basis. This system makes possible accurate data recovery, whether a transponder has its output shorted, or although multiple transponders are replying and makes possible the remote determination and constant monitoring of transducer sensitivity, at the controller. The sensitivity can be adjusted remotely at the controller, and different transducers can have different thresholds simultaneously, which can be changed collectively or individually to different settings manually or automatically at the controller. The system transmits reference data for supervision of system accuracy. Compensation for long-term changes is provided for both transponders and transducers in this system.

Abstract: A communication system useful for fire detection which transfers data/commands bidirectionally between a controller and connected transponders on a real time, interactive basis. This system makes possible accurate data recovery, whether a transponder has its output shorted, or although multiple transponders are replying and makes possible the remote determination and constant monitoring of transducer sensitivity, at the controller. The sensitivity can be adjusted remotely at the controller, and different transducers can have different thresholds simultaneously, which can be changed collectively or individually to different settings manually or automatically at the controller. The system transmits reference data for supervision of system accuracy. Compensation for long-term changes is provided for both transponders and reducers in this system.

Abstract: The signalling system disclosed herein transmits groups of pulses to a plurality of transponders, and each transponder recognizes its address in a particular group of pulses. The group of pulses can reset the system, command a transponder to accomplish a specific function, or command the transponder to do nothing. Information returned from the transponder includes a reference voltage, which can be compared in the controller to continuously determine the margin from alarm of an associated transducer. The transponder further provides a signal identifying itself, and pulse duration signals representing analog signals received from one or more transducers associated with the transponders. No end-of-line termination is required, and branching is possible at any point along the loop.

Abstract: A seismic sensor for intrusion detection includes a base, a cantilever member of piezoelectric construction extending from the base, and a mass loading the end of the cantilever member remote from the base. The base defines a slot for receiving the end of the cantilever member, and holes, perpendicular to the slot, for receiving electrical conductors. These conductors are configured to orient the cantilever member at 45.degree. relative to the horizontal, providing a sensitivity in both the X direction and the Y direction. A housing encloses the sensor, and another leg extends from the housing at the end remote from the base, enhancing the mechanical coupling between the sensor and the surface on which it is supported.

Abstract: An intrusion detection system includes a vibration sensor, and a gate circuit operable to provide an output signal only after the vibration sensor produces a first signal, and thereafter a second, separate signal within a preassigned "sensing window" period. To accomplish this, a timer circuit initiated by the sensor determines a timing interval, and a delay circuit coupled to the timing circuit prevents switching of the gate circuit until preset delay time has elapsed. After the delayed time, if a second sensor output signal is received before expiration of the timing interval, the gate circuit switches and passes a signal through an integrated circuit amplifier stage, and a driver circuit to energize an output unit. The sensitivity of the vibration sensor can be adjusted. The integrated circuit stage includes circuitry for maintaining the alarm signal even if the system is switched to off after it goes into alarm.